1. Field of the Invention
This invention relates to a rimmed wheel of a generally disc type for use in vehicles, particularly truck, bus and light-weight truck. More particularly, it relates to an improvement in a rimmed wheel which is mounted to a vehicle by driving a flanged hexagon nut into a hub bolt at a disc portion of the rimmed wheel, whereby the fatigue endurance of the disc portion is improved.
2. Description of the Prior Art
The rimmed wheel is mounted to the vehicle by clamping the disc portion through a hub bolt and a flanged hexagon nut fitted to a threaded leg thereof, wherein a plurality of straight circle holes or bolt holes each having an equal inner diameter over its entire length are formed in the disc portion at given intervals along a pitch circle coaxial to the disc portion. During the running of the vehicle, however, an external force applied to the disc portion repeatedly concentrates in an outer flange edge of the flanged hexagon nut, particularly outward the pitch circle arranging the bolt holes, where fatigue failure is frequently caused.